Sounds like a concept dreamed up by an insane person. Like 'Pete's Dragon' with Hitler as the dragon.
Seriously, this is going to cause a LOT of ruffled feathers.
A lovable, goofy imaginary friend Hitler? How could anyone think it was a good idea to make a kinder, gentler Hitler? What kind of drugs were they on? I actually think the movie looks hilarious, but I have the good sense to know it will have a very negative reaction from many people.
Most millennials barely even understand who Hitler was, anyway, so turning him into Calvin & Hobbes is really not the best plan. They'll go home full of fuzzy, warm feelings for Der Fuhrer.